Recent sliding devices have been needed to meet anticipated design specifications in extensively increased fields as diverse as machine tools, semiconductor manufacturing equipments, various assembling machines, testing instruments, and so on. An example of the sliding device compact or slim in construction is disclosed in, for example the Japanese Patent Laid-Open No. H11-30234 in which a guide rail is made of a pair of lengthwise sides joined together with one another while a lengthwise lead screw is carried at forward and aft ends thereof with bearing blocks that are rested above the guide rail. A slider is detachably connected with a ball nut mating with the lead screw to move on the guide rail in a sliding manner. The sliding device as recited earlier is made easier in disassembling/reassembling works to perform the maintenance or change the guide rail in length, the lead screw in lead or diameter, and the like, and further made readily in various operations to mount the bearing blocks on the guide rail.
With the sliding device constructed as stated earlier, nevertheless, the slider is raised higher because the lead screw to force the slider relatively to the guide rail is laid above the slider that fits into the guide rail, whereby the sliding device would become tall in the overall height from the bottom of the guide rail to the top surface of the slider. Thus, the prior sliding device could not be availed in the site constrained in height dimension. This means that the prior sliding devices of the type constructed as stated earlier are not ready for the appliance less in the overall height.
Further for example in the Japanese Patent Laid-Open No. 2002-174317 there is disclosed an actuator in which a ball-nut screw unit is combined detachably with a machine frame. With the prior actuator recited above, a slider is recessed at the top surface thereof in the form of U-shape in transverse section, which extends in the axial direction of the slider to allow the ball-nut screw unit to fit detachably into the recess from above. In the slider of the actuator, there is made at the recess a rectangular window open to the bottom of the slider to accommodate therein a return tube where balls are allowed to roll through there to force the ball nut to move forward and backward along the lead screw. This construction as stated earlier helps reduce the overall height of the slider.
The prior actuator made therein with the window for the return tube as well as the U-shape recess for the ball-nut screw unit, however, would be inconvenient for the ball-nut screw units, which are different in design specifications. Moreover, the slider, as much material being removed to make the recess and window, would get less in mechanical stiffness, unavailable for the appliances large in load capacity.
A linear motion guide unit is disclosed in, for example the Japanese Patent Laid-Open No. 2001-12465, which makes it possible to keep a workpiece at the desirable position and posture upon any working and/or feeding process of the workpiece. With the prior linear motion guide unit recited just above, the machine bed and the workpiece table are both provided thereon with fixed surfaces of reference, respectively, against which their associated guide rail and workpiece table are mounted with keeping accurately their preselected positions and postures, whereby the workpiece table may be well kept in the desired posture relatively to the guide rail while the workpiece table travels together with the slider along the guide rail. The prior linear motion guide unit recited above is comprised of the guide rail and the slider, which are combined together in a relation that the slider fits snugly into between widthwise opposing sides of the guide rail, but the slider head thereof rises in height above the tops of the sides of the guide rail. The guide rail is provided with a first surface of reference against which a mounting surface formed on the machine bed comes in abutment, while the slider head is provided with a second surface of reference against which a mounting surface formed on the workpiece table comes in abutment.